The present invention relates to plastic lenses for spectacles, in particular to those having a high refractive index and a high Abbe""s number and having good transparency, heat resistance, mechanical strength and impact resistance.
Plastics are being much used these days for optical products such as lenses, as being lightweight, hardly broken and easily colored when compared with glass. It is known to use, as the monomer material, an epithio group-having compound in producing plastic lenses. For example, Japanese Patent Laid-Open No. 180977/1999 discloses a plastic lens having optical properties, a refractive index of 1.70 or so and an Abbe""s number of from 35 to 37 or so, which, however, still leaves room for improving its heat resistance and mechanical strength.
Japanese. Patent Laid-Open Nos. 292950/1999 and 352302/1999 disclose a resin composition prepared by reacting an epithio group-having compound, an isocyanate group-having compound and a thiol group-having compound in a ratio of thiol group/isocyanate group of at most 1, and its use for plastic lenses. They say that the resin composition has improved heat resistance, mechanical strength and impact resistance. However, the plastic lenses of the resin composition are often cloudy and could not be well cured, and are therefore unsuitable to practical use for spectacles.
The present invention has been made so as to solve the problems as above, and to provide plastic lenses for spectacles having a high refractive index and a high Abbe""s number and having good transparency, heat resistance, mechanical strength and impact resistance.
The present Inventors have found that (1) a plastic lens produced through polymerization of an epithio group-having compound (a), a mercapto (xe2x80x94SH) group-having polythiol compound (b) and an isocyanate (xe2x80x94NCO) group-having, sulfur-free polyisocyanate compound (c0) in a ratio (by mol), xe2x80x94SH/xe2x80x94NCO, of at least 2.0; (2) a plastic lens produced through polymerization of an epithio group-having compound (a), a mercapto group-having polythiol compound (b) and an isocyanate group-having, sulfur-containing polyisocyanate compound (cs) in a ratio (by mol), xe2x80x94SH/xe2x80x94NCO, of at least 1.2 can attain the desired balance of properties.
Specifically, the first aspect of the invention is to provide a plastic lens for spectacles, which is produced through polymerization of an epithio group-having compound, a polythiol compound and a sulfur-free polyisocyanate compound in a ratio (by mol) of the polythiol compound to the sulfur-free polyisocyanate compound, xe2x80x94SH/xe2x80x94NCO, of at least 2.0.
The second aspect of the Invention is to provide a plastic lens for spectacles, which is produced through polymerization of an epithio group-having compound, a polythiol compound and a sulfur-containing polyisocyanate compound in a ratio, (by mol) of the polythiol compound to the sulfur-containing polyisocyanate compound, xe2x80x94SH/xe2x80x94NCO, of at least 1.2.
The polyisocyanate compound (c) may be a mixture of a sulfur-containing polyisocyanate compound (cs) and a sulfur-free polyisocyanate compound (c0). The plastic lens material may be produced through polymerization of at least one polyisocyanate compound selected from di(isocyanatomethyl)bicycloheptane, bis(isocyanatomethyl)-1,4-dithian and dicyclohexylmethane diisocyanate, and an, epithio group-having compound and a polythiol compound. The plastic lens material may also be produced through polymerization of a polyisocyanate compound prepared by mixing bis(isocyanatomethyl)-1,4-dithian with di(isocyanatomethyl)bicycloheptane and/or dicyclohexylmethane diisocyanate, and an epithio group-having compound and a polythiol compound.
In its first aspect, the plastic lens for spectacles of the invention is produced through polymerization of an epithio group-having compound, a polythiol compound and a sulfur-free polyisocyanate compound in a ratio (by mol) of the polythiol compound to the sulfur-free polyisocyanate compound, xe2x80x94SH/xe2x80x94NCO, of at least 2,0. If the ratio xe2x80x94SH/xe2x80x94NCO is smaller than 2.0, the effect of the first aspect of the invention cannot be obtained.
In its second aspect, the plastic lens for spectacles of the invention is produced through polymerization of an epithio group-having compound, a polythiol compound and a sulfur-containing polyisocyanate compound in a ratio (by mol) of the polythiol compound to the sulfur-containing polyisocyanate compound, xe2x80x94SH/xe2x80x94NCO, of at least 1.2. If the ratio xe2x80x94SH/xe2x80x94NCO is smaller than 1.2, the effect of the invention cannot be obtained. Polyisothiocyanate group-having compounds are outside the scope of the sulfur-containing polyisocyanate compound, as not producing then advantages of the invention.
With the increase in the proportion of thiourethane bonds therein, lenses for spectacles could have an increased tensile strength characteristic of polythiourethanes, but their refractive index could not increase. For further increasing the refractive index of the lenses while producing lenses having an increased tensile strength and an increased Abbe""s number, heretofore proposed is adding an epithio group-having compound to the lenses. However, in the system for lenses that comprises an epithio group-having compound, a polythiol compound and a sulfur-free polyisocyanate compound, if the polyisocyanate is excessive over the polythiol, as in the Examples in Japanese Patent Laid-Open Nos. 180977/1999 and 292950/1999, the lenses formed are cloudy.
On the other hand, lenses formed from a sulfur-containing polyisocyanate compound, an epithio group-having compound and a polythiol compounds are not cloudy even when the proportion of the sulfur-containing polyisocyanate compound therein is increased. Since the sulfur content and the thiourethane bond content thereof are high, the lenses have an increased refractive index and their mechanical strength and Abbe""s number are not lowered.
Some sulfur-containing polyisocyanate compounds such as bis(isocyanatomethyl)-1,4-dithian are solid at room temperature. Such a solid, sulfur-containing polyisocyanate compound may be dissolved in a sulfur-free polyisocyanate compound that is liquid at room temperature. As being liquid at room temperature, the resulting mixture is easy to handle when it is used in producing lenses. In mixing the two, the ratio of the sulfur-containing polyisocyanate compound to the sulfur-free polyisocyanate compound may be so controlled that the liquid, sulfur-free polyisocyanate compound can dissolve the solid, sulfur-containing polyisocyanate compound to give a mixture that is liquid at room temperature. In practice, the ratio of the sulfur-containing polyisocyanate compound and the sulfur-free polyisocyanate compound may be such that the amount of the sulfur-free polyisocyanate compound is enough for dissolving therein the sulfur-containing polyisocyanate compound which is solid at room temperature. The ratio of the two can be readily determined to produce lenses having the desired balance of properties. For example, from 5 to 30 parts by weight of a sulfur-free polyisocyanate may be added to 10 parts by weight of a sulfur-containing polyisocyanate.
A sulfur-free polyisocyanate compound that can be used in the first and second aspects of the invention is di(isocyanatomethyl)bicycloheptane and/or dicyclohexylmethane diisocyanate. A sulfur-containing polyisocyanate compound that can be used is bis(isocyanatomethyl)-1,4-dithian.
The lens for spectacles may be produced through polymerization of at least one polyisocyanate compound selected from di(isocyanatomethyl)bicycloheptane, bis(isocyanatomethyl)-1,4-dithian and dicyclohexylmethane diisocyanate, and an epithio group-having compound and a polythiol compound. The lens for spectacles may also be produced through polymerization of a polyisocyanate compound prepared by mixing bis(isocyanatomethyl)-1,4-dithian with di(isocyanatomethyl)bicycloheptane and/or dicyclohexylmethane diisocyanate, and an epithio group-having compound and a polythiol compound.
Bis(isocyanatomethyl)-1,4-dithian is solid at room temperature. When it is mixed with di(isocyanatomethyl)bicycloheptane and/or dicyclohexylmethane diisocyanate, and dissolved therein, the resulting mixture is liquid at room temperature, and is easy to handle.
The ratio (by mol) of the polythiol compound to the polyisocyanate compound, xe2x80x94SH/xe2x80x94NCO, is preferably at least 2.0, more preferably at least 2.5.
The polythiol compound for use in the invention includes, for example, aliphatic thiols such as methanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanedithiol, 1,2,3-propanetrithiol, tetrakis(mercaptomethyl)methane, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol, 2,2dimethylpropane-1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol, 2-methylcyclohexane-2,3-dithiol, 1,1-bis(mercaptomethyl)cyclohexane, bis(2-mercaptoethyl)thiomalate, (2-mercaptoethyl) 2,3-dimercaptosuccinate, 2,3-dimercapto-1-propanol (2-mercaptoacetate), 2,3-dimercapto-1-propanol (3-mercaptoacetate), diethylene glycol bis(2-mercaptoacetate), diethylene glycol bis(3-mercaptopropionate), 1,2-dimercaptopropyl methyl ether, 2,3-dimercaptopropyl methyl ether, 2,2-bis(mercaptomethyl)-1,3-propanedithiol, bis(2-mercaptoethyl) ether, ethylene glycol bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane; aliphatic thiols having sulfur atom(s) in addition to mercapto groups, such as bis(mercaptomethyl) sulfide, bis(mercaptoethyl) sulfide, bis(mercaptopropyl) sulfide, bis(mercaptomethylthio)methane, bis(2-mercaptoethylthio)methane, bis(3-mercaptopropyl)methane, 1,2-bis(mercaptomethylthio)ethane, 1,2-(2-mercaptoethylthio)ethane, 1,2-(3-mercaptopropyl)ethane, 1,3-bis(mercaptomethylthio)propane, 1,3-bis(2-mercaptoethylthio)propane, 1,3-bis(3-mercaptopropylthio)propane, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 2-mercaptoethylthio-1,3-propanedithiol, 1,2,3-tris(mercaptomethylthio)propane, 1,2,3-tris(2-mercaptoethylthio)propane, 1,2,3-tris(3-mercaptopropylthio)propane, tetrakis(mercaptomethylthiomethyl)methane, tetrakis(2-mercaptoethylthiomethyl)methane, tetrakis(3-mercaptopropylthiomethyl)methane, bis(2,3-dimercaptopropyl) sulfide, 2,5-dimercapto-1,4-dithian, bis(mercaptomethyl) disulfide, bis(mercaptoethyl) disulfide, bis(mercaptopropyl) disulfide, and their thioglycolates and mercaptopropionates,hydroxymethylsulfide bis(2-mercaptoacetate), hydroxymethy bis(3-mercaptopropionate), hydroxyethylsulfide bis(2-mercaptoacetate), hydroxyethylsulfide bis(3-mercaptopropionate), hydroxypropylsulfide bis(2-mercaptoacetate), hydroxypropylsulfide bis(3-mercaptopropionate), hydroxymethyldisulfide bis(2-mercaptoacetate), hydroxymethyldisulfide bis(3-mercaptopropionate), hydroxyethyldisulfide bis(2-mercaptoacetate), hydroxyethyldisulfide bis(3-mercaptopropionate), hydroxypropyldisulfide bis(2-mercaptoacetate), hydroxypropyldisulfide bis(3-mercaptopropionate), 2-mercaptoethyl-ether bis(2-mercaptoacetate), 2-mercaptoethyl-ether bis(3-mercaptopropionate), 1,4-dithian-2,5-diol bis(2-mercaptoacetate), 1,4-dithian-2,5-diol bis(3-mercaptopropionate), bis(2-mercaptoethyl)thioglycolate, bis(2-mercaptoethyl)thiodipropionate, bis(2-mercaptoethyl) 4,4xe2x80x2-thiodibutyrate, bis(2-mercaptoethyl) dithiodiglycolate, bis(2-mercaptoethyl) dithiodipropionate, bis(2-mercaptoethyl) 4,4xe2x80x2-dithiodibutyrate, bis(2,3-dimercaptopropyl)thioglycolate, bis(2,3-dimercaptopropyl)thiodipropionate, bis(2,3-dimercaptopropyl)dithiodiglycolate, (2,3-dimercaptopropyl)dithiodipropionate, 4-mercaptomethyl-3,6-dithiaoctane-1,8-dithiol, bis(mercaptomethyl)-3,6,9-trithia-1,11-undecanedithiol, bis(1,3-dimercapto-2-propyl)sulfide; and heterocyclic compounds having sulfur atom(s) in addition to mercapto groups, such as 3,4-thiophenedithiol, tetrahydrothiophene-2,5-dimercaptomethyl, 2,5-dimercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,4-dithian, 2,5-dimercaptomethyl-1,4-dithian.
The polythiol compound for use in the invention is preferably bismercaptomethyl-1,4-dithian and/or (4-mercaptomethyl-2,5-dithianyl)methyl disulfide.
The epithio group-having compound for use in the invention is an episulfide monomer, including, for example, alicyclic skeleton-having episulfide compounds such as 1,3- and 1,4-bis(xcex2-epithiopropylthio)cyclohexanes, 1,3- and 1,4-bis(xcex2-epithiopropylthiomethyl)cyclohexanes, bis[4-(xcex2-epithiopropylthio)cyclohexyl]methane, 2,2-bis[4-(xcex2-epithiopropylthio)cyclohexyl]propane, bis[4-(xcex2-epithiopropylthio)cyclohexyl]sulfide; aromatic skeleton-having episulfide compounds such as 1,3- and 1,4-bis(xcex2-epithiopropylthio)benzenes, 1,3- and 1,4-bis(xcex2-epithiopropylthiomethyl)benzenes, bis[4-(xcex2-epithiopropylthio)phenyl]methane, 2,2-bis[4-(xcex2-epithiopropylthio)phenyl]propane, bis[4-(xcex2-epithiopropylthio)phenyl]sulfide, bis[4-(xcex2-epithiopropylthio)phenyl]sulfide, 4,4-bis(xcex2-epithiopropylthio)biphenyl; dithian skeleton-having episulfide compounds such as 2,5-bis(xcex2-epithiopropylthiomethyl)1,4-dithian, 2,5-bis(xcex2-epithiopropylthioethylthiomethyl)-1,4-dithian, 2,5-bis(xcex2-epithiopropylthioethyl)-1,4-dithian, 2,3,5-tri(xcex2-epithiopropylthioethyl)-1,4-dithian; and aliphatic skeleton-having episulfide compounds such as 2-(2-xcex2-epithiopropylthioethylthio)-1,3-bis(xcex2-epithiopropylthio)propane, 1,2-bis[(2-xcex2-epithiopropylthioethyl)thio]-3-(xcex2-epithiopropylthio)propane, tetrakis(xcex2-epithiopropylthiomethyl)methane, 1,1,1-tris(xcex2-epithiopropylthiomethyl)propane, bis(xcex2-epithiopropyl)sulfide.
Many epithio group-having compounds are known, and their examples are described in, for example, Japanese Patent Laid-Open Nos. 071580/1997, 110979/1997, 255781/1997, 081320/1991, 140070/1999, 183702/1999, 189592/1999, 180977/1999, and Japanese Patent Re-Laid-Open No. 810575/1989. Episulfide monomers disclosed in these publications are all usable in the invention.
Of the epithio group-having compounds mentioned hereinabove, bis(xcex2-epithiopropyl)sulfide is preferred for use in the invention.
Plastic lenses for spectacles of the invention preferably contain from 60 to 85% by weight of the epithio group-having compound and from 15 to 40% by weight of the polythiol compound and the balance polyisocyanate compound. Plastic lenses are produced that have a refractive index of 1.70 or so and an Abbe""s number of 36 or so and their mechanical strength is enough for practical use of the lenses in rimless spectacles.
Especially preferred combinations of the polyisocyanate compound, the polythiol compound and the epithio group-having compound for use in the invention are mentioned below.
A. Di(isocyanatomethyl)bicycloheptane (polyisocyanate compound), bis(mercaptomethyl)-1,4-dithian (polythiol compound), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
B. Di(isocyanatomethyl)bicycloheptane (polyisocyanate compound), (4-mercaptomethyl-2,5-dithianyl)methyl disulfide, bis(mercaptomethyl)-1,4-dithian (polythiol compounds), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
C. Bis(isocyanatomethyl)-1,4-dithian (polyisocyanate compound), bis(mercaptomethyl)-1,4-dithian (polythiol compound), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
D. Dicyclohexylmethane diisocyanate (polyisocyanate compound), (4-mercaptomethyl-2,5-dithianyl)methyl disulfide, bis(mercaptomethyl)-1,4-dithian (polythiol compounds), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
E. Bis(isocyanatomethyl)-1,4-dithian and di(isocyanatomethyl)bicycloheptane (polyisocyanate compounds), bis(mercaptomethyl)-1,4-dithian (polythiol compound), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
F. Bis(isocyanatomethyl)-1,4-dithian and dicyclohexylmethane diisocyanate (polyisocyanate compounds), bis(mercaptomethyl)-1,4-dithian (polythiol compound), and bis(xcex2-epithiopropyl)sulfide (epithio group-having compound).
The polymerization reaction according to the present invention may be performed in the presence of a catalyst. Any suitable catalyst may be employed. Specific examples of a suitable catalyst include amines such as aliphatic and aromatic tertiary amines, Lewis acids and dialkyl tin salts such as dibutyltin dichloride and dibutyltin dilaurate.
Preferably, a catalyst of the following general formula (1) is added to the plastic lenses for spectacles of the invention while they are produced through polymerization. The catalyst facilitates the production of lenses with neither optical strain nor striae from the polymerizing compounds, epithio group-having compound, polythiol compound and polyisocyanate compound. 
wherein R indicates an alkyl group having from 1 to 4 carbon atoms. The catalyst of formula (1) is preferably at least one selected from tetramethyldiacetoxy-distannoxane, tetraethyidiacetoxy-distannoxane, tetrapropyldiacetoxy-distannoxane and tetrabutyldiacetoxy-distannoxane.
In case where the plastic lenses of the invention are, after produced through polymerization in a mold, difficult to release from the mold, any known external and/or internal lubricant may be used for them or may be added to them to thereby improve the releasability of the lenses. If desired, an UV absorbent may be added to the lenses while they are produced. This is for protecting the resin of the lenses from UV rays and also for protecting the eye from them, and its amount to be added to each lens may fall generally between 0.03% and 3% or so, though depending on its UV absorbability and on the maximum wavelength of the UV rays to be absorbed by it. As the case may be, the lenses produced may be dipped in an UV absorbent. The plastic lenses of the invention are easy to color with a colorant.
For improving their scratch resistance, the plastic lenses of the invention may be coated with a hard film, for which is usable a coating liquid that contains an organosilicon compound or acrylic compound and inorganic fine particles of, for example, tin oxide, silicon oxide, zirconium oxide or titanium oxide. For improving their impact resistance, the plastic lenses may be coated with a primer layer that consists essentially of polyurethane.
For preventing them from glaring, the hard film of the plastic lenses may be further coated with an anti-glare film that contains an inorganic substance of, for example, silicon oxide, titanium dioxide, zirconium oxide or tantalum oxide. For improving their water repellency, the anti-glare film of the plastic lenses may be coated with a water-repellent film of an organic fluorosilicon compound.
The plastic lenses for spectacles of the invention mentioned hereinabove have a refractive index of from 1.65 to 1.76, and their mechanical strength is higher than that of conventional plastic lenses. In addition, they are highly transparent, and have good heat resistance and impact resistance.